1. Technical Field
The present invention relates to a safety flint lighter constructed such that a child is not allowed to ignite a flame.
2. Description of the Related Art
The flint lighters, having a tank body having a nozzle and filled with a liquefied gas fuel, a flint and a spark producing wheel, are cheap in price and hence broadly used.
The flint lighter like this has a tank body small in size and filled with a liquefied gas such as butane. At one end of the tank body, there are provided a receptor to receive therein a flint together with a flint spring, and a frame to mount an igniter thereon.
On the frame, attached are a windshield, a nozzle having a shut-off valve and a gas lever to be operated by a user's finger so that the nozzle having the shut-off valve can be operated to open and close the shut-off valve. Furthermore, a sparking file wheel is provided which has a steel-made cylindrical sparking file having saw-like teeth in a periphery thereof, side wheels coaxially attached on the side surfaces of the sparking file and having a somewhat greater diameter, and a rotary shaft, which sparking file wheel is arranged rotatable such that the sparking file contacts with one end of the flint.
The flint, inserted together with the flint spring in the receptor, is biased toward the tip of the saw-like teeth provided in the sparking file periphery of the sparking file wheel, by the elastic force of the flint spring. When a user rotates the side wheels of the sparking file wheel by his/her finger, friction is caused at the end surface of the flint by the tooth of the sparking file, to produce a spark.
Immediately after this, the user's finger goes off the side wheels and pushes down the operation lever at its one end.
The operation lever, at the tip, raises the nozzle and places one end thereof away from a valve seat of the shut-off valve. Due to this, gas is allowed to exit at the tip of the nozzle and ignited by a spark.
When the user releases the operation lever, the emission nozzle returns to close the shut-off valve thereby putting out the flame.
Because the lighter like this is to stimulate child's curiosity, there is a need to provide a safety device so that ignition cannot be caused without permission even if a child mischievously plays therewith.
For the safety device, a lock mechanism is required to be provided with any means such that the sparking file wheel cannot be rotated easily.
There are proposed various methods on such lock mechanisms.
Those include one method that the axial holes, supporting the rotary shaft of the sparking file wheel, are provided as holes in an elongate circular form or in an inverted-U form. The rotary shaft is held to move from one end to the other end of the axial holes. When the rotary shaft lies at the one end, the sparking file wheel is restricted from rotating or no sparks are caused even if it is rotated. When it lies at the other end on the opposite side, the sparking file wheel is permitted to rotate so that a spark can be caused by rotation. When a child tries an ignition imitating the adult, the rotary shaft is held at the one end or moved there where ignition cannot be caused. On the contrary, an adult is to easily move the rotary shaft to the other end where an ignition can be caused.
Besides, there is proposed another method that the sparking file wheel is structured to be rotated only by the adult's finger, not by the child's finger.
Those proposals are disclosed in JU-B-S64-54668, Japanese Patent No. 2,779,914 and U.S. Pat. No. 5,769,625.
In JU-B-S64-54668, the axial holes are made in elongate slits that the sparking file wheel is normally positioned at an axial hole end on the side distant from the lighter body by the elastic force of the flint spring applied through the flint. In this position, the sparking file wheel is locked from rotating by the windshield. Even if a child tries to rotate the sparking file wheel imitating an adult, it cannot be rotated. However, when the adult uses the lighter, the sparking file wheel can be pushed down by the finger and unlocked from the windshield. Due to this, ignition is permitted by allowing the sparking file wheel to rotate in its rotatable position.
However, in this method, the windshield is problematically to be destroyed if the sparking file wheel is rotated in a rocked state. In addition, there is also a problem that the effect is not sustainable because a child is to learn how to ignite a flame.
In the method described in Japanese Patent No. 2,779,914, the axial holes for the sparking file wheel are formed in an inverted-U form or in an inverted-heart form so that the rotary shaft can reciprocate between a movement end (hereinafter, referred to as a first position) closer to the nozzle and a movement end (hereinafter, referred to as a second position) opposite to that position. The rotary shaft is normally raised to a neutral position intermediate between the both ends by means of the elastic force of the flint spring applied to the flint. When the rotary shaft is in the first position, it is kept in a normal position relative to the flint thus permitting a normal ignition. When moved to the second position, the rotary shaft is misaligned with the flint. The sparking file wheel is prevented from rotating by a corner of the flint, thus being not permitted to ignite a flame.
With this structure, in case a child rotates the sparking file wheel in order to ignite a flame, the rotary shaft is pushed in the second position before the sparking file wheel starts rotating, thus preventing the sparking file wheel from rotating.
When igniting a flame on the lighter, the rotary shaft is pushed in the second position by first rotating the sparking file wheel in a direction reverse to the direction toward the usual ignition, in which position the sparking file wheel is rotated toward the usual ignition. In this position, the sparking file wheel rotates smoothly to produce a spark, thus effecting an ignition.
However, this scheme requires two stages of igniting operations, thus being unpopular. Moreover, it is problematically comparatively easy for a child to master through experience how to ignite a flame. Hence, this scheme is not placed in practical application.
The method described in U.S. Pat. No. 5,769,625 is a combination of the following two means.
In the first means, the axial holes for the sparking file wheel are made in an elongate circular form with respect to the axis of the flint so that the rotary shaft can be movably held in a first position distant from the lighter body and a second position closer to the body. The rotary shaft is normally held in the first position by the elastic force of the flint spring. In the first position, even if the sparking file wheel rotates, the elastic force of the flint spring is weak thus not causing a spark, to prevent an ignition of a flame. When pushed down to the second position, a strong elastic force acts upon the flint so that rotating the sparking file wheel in that position produces a spark thus causing an ignition of a flame.
In the second means, the side wheel of the sparking file wheel is finished smooth in its outer peripheral surface while properly determining the diametrical difference between the side wheel and the sparking file as well as the width of the sparking file so that the serrated surface of the sparking file can be contacted only by an adult's finger having plenty of flexible muscles.
Namely, because the sparking file serration cannot be contacted by a child's finger with less flexible muscle, the child is not allowed to rotate the sparking file to ignite a flame.
However, this method is problematic in that there is a difficulty in determining the diametrical difference between the side wheel and the sparking file as well as the width of the sparking file, thus resulting in a difficulty in achieving the desired object. The stiffness and smoothness of finger's skin and muscles greatly differs in person to person. If ignition is not allowed perfectly for the child, ignition is made impossible for the women and aged persons whose fingers are thin.